A multi-scale approach to identifying the ecological impact of co-occurring environmental stressors

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Freshwater resources are critical to Canada's economy and cultural identity. Over 70% of the drinking water in Ontario comes from surface waters, and recreational fisheries across Canada contribute $8.3 billion to local economies. Despite this, human activities are dramatically altering species composition in freshwater habitats, which threatens ecosystem function and the provision of valuable services. An abundance of research has looked at the impact of individual environmental stressors (e.g., nutrients, temperature) on ecosystem function, although often at a single scale, e.g., individual or community. Our ability to predict community and ecosystem response to multiple, co-occurring stressors is significantly limited because few studies consider multiple stressors, which is problematic for ecosystem management because stressors often interact such that their combined effect is greater (or less) than the simple sum of each stressor. Even fewer studies examine whether individual life history responses scale up to changes in ecosystem function, despite management targets aimed at the ecosystem level. My proposed research addresses this challenge by testing two approaches for predicting changes in ecosystem function; 1) scaling up from life history responses in key species to predict ecosystem function, and 2) predicting ecosystem function based on community traits such as species or functional diversity. We will conduct multi-scale experiments and develop models to critically evaluate these approaches using 5 important environmental stressors in Ontario lakes; increasing chloride (from road salt), decreasing calcium, nutrient loading, increasing temperature and the spread of non-native species. We focus on zooplankton because they can control algal populations (relevant for drinking water quality) and provide energy for higher trophic levels (relevant for fisheries). Zooplankton communities are ideal for multi-scale experiments because they have short generation times, can be grown as individuals under laboratory conditions as well as in diverse, multi-trophic communities under field conditions, and they exhibit a range of tolerances to environmental stressors. Our research will provide scientists and managers tools for predicting the impact of multiple stressors on community structure and ecosystem function, in lieu of the almost impossible task of experimentally evaluating ecosystem response to every possible stressor combination. This will help managers and policy-makers prioritize conservation of valuable ecosystem services. This research program will train 3 PhD, 3 MSc, 1 PDF and at least 15 BSc students in ecotoxicology, field studies, taxonomy, experimental design, statistical analyses, physiological modelling, communication, and collaboration. These are highly sought skills in environmental fields, but also transfer to other careers that require critical thinking, quantitative skills, communication, and strong leadership.